1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device and, more particularly, to a method of manufacturing a CMOS semiconductor device.
2. Description of the Related Art
In the manufacture of a semiconductor device such as a CMOS device, a tendency toward further micro-patterning and higher density of the circuit is prominent. In this case, a so-called scaling rule law is applied, and the concentrations of a substrate, a well, and a diffusion layer tend to be increased with the tendency toward further micropatterning and higher density of the circuit.
Several factors are assumed to determine an operation speed of a device. In particular, in a logic device, a capacitance of a diffusion layer defined by a depletion layer formed in a p-n junction between a diffusion region and a substrate, or between a diffusion region and a well is a major factor. More specifically, when a capacitance of a diffusion layer is increased, a speed of the device is decreased. In general, when the concentrations of a substrate and a well near p-n junctions are increased, the width of the depletion layer is decreased, thereby increasing a capacitance of the diffusion layer. Therefore, with the tendency toward further micropatterning and higher density of the circuit, a speed of the device is undesirably reduced.
If the concentration of the substrate is increased, an electric field applied to the depletion layer of a p-n junction becomes high, and hence probability of generation of a so-called hot carrier is increased, thus causing degradation in reliability of the device.
When the circuit is micropatterned, the depth of the diffusion layer is decreased. In this case, a metal wiring layer undesirably penetrates into the substrate from the diffusion layer. Thus, in a conventional method of manufacturing a CMOS semiconductor device, when an attempt is made to micropattern and increase the density of the circuit, a speed of the device may be reduced, or a metal wiring layer may penetrate into the substrate from the diffusion layer.